Liquid crystal display device having stocked pixel layers

ABSTRACT

A liquid crystal display device including a plurality of pixel electrodes and a plurality of liquid crystal layers stacked alternately. A shield electrode is disposed below the lowest pixel electrode. Potential differences are applied to liquid crystal layers other than the uppermost liquid crystal layer by supplying potentials to the respective pixel electrodes. Thereafter, the pixel electrodes other than the uppermost pixel electrode are rendered in a floating state, and a prescribed potential difference is applied to the uppermost liquid crystal layer by supplying a proper potential to the uppermost pixel electrode. A potential corresponding to the potential that is supplied to the uppermost pixel electrode is applied to the shield electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Application No. 10-071606filed Mar. 20, 1998, the entire content of which is hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device and, inparticular, to a stack-type liquid crystal display device having stackedliquid crystal layers.

2. Discussion of the Background

Being thin and of low power consumption, liquid crystal display devicesare now widely used in notebook-sized personal computers. In particular,the low power consumption is a feature that makes liquid crystal displaydevices superior to other displays such as CRT displays and plasmadisplays. Liquid crystal display devices are expected to be increasinglywidely applied to personal information equipment in the future.

In portable equipment, it is desirable that the power consumption of thedisplay be 500 mW or less, preferably as low as several milliwatts.Consequently, the reflection-type liquid crystal display device isdesirable because it does not require a backlight and is of low powerconsumption. Among reflection-type color liquid crystal display devicesare the in-plane type devices using color filters. However, if the colorpurity in these devices is improved, the light utilization efficiency islowered by a factor of three or more, and hence the reflectance isdecreased.

In view of the above, stack/reflection-type liquid crystal displaydevices having stacked liquid crystal layers have been proposed (referto Japanese Unexamined Patent Publication No. Hei. 8-313939, forexample). In the reflection-type liquid crystal display device disclosedin the publication No. Hei. 8-313939, guest-host liquid crystal layersof cyan, magenta, and yellow are used. To apply potential differences tothe respective liquid crystal layers, pixel electrodes are provided sothat each liquid crystal layer is interposed in between and an activematrix substrate is provided under each liquid crystal layer. The pixelelectrodes are connected to respective active elements such as TFTs viacolumnar electrodes. A desired display image is produced by applyingprescribed potential differences to the respective liquid crystal layersin the form of potential differences between the pixel electrodes.Although this type of stack-type liquid crystal display device enableshigh light utilization efficiency and hence can provide a brightreflection image, it requires the application of differential potentialdifferences to the respective liquid crystal layers in the driving ofthe pixels.

Japanese Unexamined Patent Publication No. Hei. 9-80488 has proposed onemethod of applying differential potential differences, in whichdifferential potential differences are generated in a pixel by drivingpixel layers (sub-pixels) in a time-divisional manner (time-divisionaldifferential driving) and rendering the other pixel layers in a floatingstate when a potential difference is applied to one pixel layer.However, the potentials of pixel electrodes that are rendered in afloating state tend to vary due to coupling with scanning lines, signallines, or the like, possibly resulting in deterioration in image qualitysuch as crosstalk.

Further, as for the use of auxiliary capacitors in the time-divisionaldifferential driving, sufficient studies have not been made of how toconnect and arrange the auxiliary capacitors to effectively reduce thedegree of coupling with scanning lines and signal lines.

As described above, in conventional liquid crystal display devices thatdisplay by applying prescribed potential differences to the respectivestacked pixel layers (sub-pixels) in a time-divisional manner, effectivemeasures have not been taken in terms of the driving technique, thelayout of auxiliary capacitors. and other techniques in order to reducethe degree of coupling with scanning lines and signal lines that areprovided on the lower-layer side.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems in theart. Therefore, in a liquid crystal display device that displays byapplying prescribed potential differences to respective stacked pixellayers in a time-divisional manner, an object of the present inventionis to reduce the degree of coupling with scanning lines and signal linesprovided on the lower-layer side. In other words, an object of thepresent invention is to shield the liquid crystal layers from scanningand signal lines.

A liquid crystal display device according to the present inventioncomprises a plurality of pixel electrodes and a plurality of liquidcrystal layers that are stacked alternately, a shield electrode that isdisposed below the lowest pixel electrode, and a circuit for supplyingthe shield electrode with a potential corresponding to a potential thatis supplied to the uppermost pixel electrode.

The uppermost and lowest pixel electrodes are the uppermost and lowestones of the stacked pixel electrodes that function substantially toapply prescribed potential differences to the respective liquid crystallayers.

The circuit for supplying the shield electrode with a potentialcorresponding to a potential that is supplied to the uppermost pixelelectrode may short circuit the shield electrode to the uppermost pixelelectrode.

In the liquid crystal display device of the present invention, afterprescribed potentials have been applied to the respective liquid crystallayers other than the uppermost liquid crystal layer by supplyingpotentials to the respective pixel electrodes, the pixel electrodes thathave served to apply the prescribed potential differences are renderedin a floating state, and prescribed potentials are applied to theuppermost pixel electrode and the shield electrode.

It is preferable to provide a common electrode in such a manner that theuppermost liquid crystal layer is interposed between the uppermost pixelelectrode and the common electrode (the uppermost liquid crystal layeris disposed above the uppermost pixel electrode). In this case, aprescribed potential difference may be applied to the uppermost liquidcrystal layer by supplying prescribed potentials to the uppermost pixelelectrode and the common electrode.

In the above liquid crystal display device, after potential differencescorresponding to display signals have been applied to the liquid crystallayers other than the uppermost liquid crystal layer, the liquid crystallayers other than the uppermost liquid crystal layer are rendered in afloating state and a potential difference corresponding to a displaysignal is applied to the uppermost liquid crystal layer. At this time,the potential of the shield electrode that is disposed below the lowestpixel electrode varies in link with the potential of the uppermost pixelelectrode. Therefore, even if regions exist below the shield electrodethat are given prescribed potentials such as signal lines, scanninglines, and active elements, potential variations at the pixel electrodesdue to coupling with those regions can be inhibited. Further, thepotential differences applied to the respective liquid crystal layerscan be maintained.

Another aspect of the present invention provides a liquid crystaldisplay device having a shield electrode that is disposed below thelowest pixel electrode in which after prescribed potentials have beenapplied to the respective liquid crystal layers other than the lowestliquid crystal layer, the pixel electrodes other than the lowest pixelelectrode are rendered in a floating state, and a prescribed potentialdifference is applied to the lowest liquid crystal layer by supplyingproper potentials to the lowest pixel electrode and the shieldelectrode. In this liquid crystal display device, after potentialdifferences corresponding to display signals have been applied to theliquid crystal layers other than the lowest liquid crystal layer, theliquid crystal layers other than the lowest liquid crystal layer arerendered in a floating state and a potential difference corresponding toa display signal is applied to the lowest liquid crystal layer. At thistime, the shield electrode that is disposed below the lowest pixelelectrode has a prescribed potential. Therefore, even if regions existbelow the shield electrode that are given prescribed potentials such assignal lines, scanning lines, and active elements, potential variationsat the pixel electrodes due to coupling with those regions can beinhibited. Therefore, the potential differences applied to therespective liquid crystal layers can be maintained. It is preferablethat the shield electrode be a common electrode of the lowest liquidcrystal layer.

Another aspect of the present invention provides a liquid crystaldisplay device comprising a plurality of pixel electrodes and aplurality of liquid crystal layers that are stacked alternately, and aplurality of electrodes for auxiliary capacitors that are disposed belowthe lowest liquid crystal layer. The auxiliary capacitor electrodes canbe stacked in the order that is opposite to the stack order of thecorresponding pixel electrodes.

The lowest pixel electrode and the uppermost auxiliary capacitorelectrode may be commonized with each other; that is, a single electrodemay be provided that has the functions of those two electrodes.

Still another aspect of the present invention provides a liquid crystaldisplay device having auxiliary capacitor electrodes below the lowestliquid crystal layer in which after prescribed potentials have beenapplied to the respective liquid crystal layers other than the uppermostliquid crystal layer, the pixel electrodes other than the uppermostpixel electrode are rendered in a floating state, and proper potentialsare applied to the uppermost pixel electrode and the correspondingauxiliary capacitor electrode.

It is preferable to provide a common electrode in such a manner that theuppermost liquid crystal layer is interposed between the uppermost pixelelectrode and the common electrode (the uppermost liquid crystal layeris disposed above the uppermost pixel electrode). In this case, aprescribed potential difference may be applied to the uppermost liquidcrystal layer by supplying prescribed potentials to the uppermost pixelelectrode and the common electrode.

A further aspect of the present invention provides a liquid crystaldisplay device having a plurality of auxiliary capacitor electrodes thatare disposed below the lowest liquid crystal layer in which afterprescribed potentials have been applied to the respective liquid crystallayers other than the lowest liquid crystal layer, the pixel electrodesother than the lowest pixel electrode are rendered in a floating state,and a prescribed potential difference is applied to the lowest liquidcrystal layer by supplying proper potentials to the lowest pixelelectrode and the corresponding auxiliary capacitor electrode.

It is preferable to provide a common electrode in such a manner that thelowest liquid crystal layer is interposed between the lowest pixelelectrode and the common electrode (the lowest liquid crystal layer isdisposed below the lowest pixel electrode). In this case, a prescribedpotential difference may be applied to the lowest liquid crystal layerby supplying prescribed potentials to the lowest pixel electrode and thecommon electrode.

The auxiliary capacitor electrodes function as shields. Therefore, evenif there exist, below the lowest auxiliary capacitor electrode, regionsthat are given prescribed potentials such as signal lines, scanninglines, and active elements, potential variations at the pixel electrodesdue to coupling with those regions can be inhibited. Therefore, thepotential differences applied to the respective liquid crystal layerscan be maintained.

Since a lower pixel electrode is more influenced through coupling withunderlying regions, a higher auxiliary capacitor electrode has astronger shield effect for the pixel electrodes. If the auxiliarycapacitor electrodes are stacked in the order that is opposite to thestack order of the corresponding pixel electrodes, the lowest pixelelectrode that is influenced through the coupling most and the uppermostauxiliary capacitor electrode that has the strongest shield effect canbe given the same potential. Therefore, the coupling can be minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 shows a cross-sectional view of a display according to a firstembodiment of the present invention;

FIGS. 2-5 show cross-sectional views of a display according tomodifications of the first embodiment of the present invention;

FIG. 6 is an equivalent circuit diagram of a pixel portion according tothe first embodiment of the present invention;

FIG. 7 shows the configuration of driver circuits according to the firstembodiment of the present invention;

FIG. 8 shows the configuration of a signal line driver circuit shown inFIG. 7;

FIG. 9 shows signal waveforms at respective members according to thefirst embodiment of the present invention;

FIGS. 10 and 11 show plan layouts of array substrates according to thefirst embodiment of the present invention;

FIG. 12 is a sectional view of the array substrates of FIGS. 10 and 11;

FIG. 13 is an equivalent circuit diagram of a pixel portion according toa modification of the first embodiment of the present invention;

FIG. 14 shows the configuration of driver circuits according to themodification of the circuit of FIG. 13:

FIG. 15 is an equivalent circuit diagram of a pixel portion according toa second embodiment of the present invention;

FIG. 16 shows a plan layout of an array substrate according to thesecond embodiment of the present invention;

FIG. 17 shows the configuration of driver circuits according to thesecond embodiment of the present invention;

FIG. 18 shows the configuration of a signal line driver circuit shown inFIG. 17;

FIG. 19 shows a plan layout of an array substrate according to a thirdembodiment of the present invention;

FIG. 20 is a sectional view of the array substrate of FIG. 19;

FIG. 21 is an equivalent circuit diagram used for calculating capacitivecoupling at each portion;

FIG. 22 shows a basic, conceptual configuration according to a fourthembodiment of the present invention;

FIG. 23 is an equivalent circuit diagram of a pixel portion according tothe fourth embodiment of the present invention:

FIG. 24 is an equivalent circuit diagram of another example of a pixelportion according to the fourth embodiment of the present invention;

FIG. 25 is an equivalent circuit diagram of a pixel portion of atime-divisional differential driving type liquid crystal display panel;

FIG. 26 shows drive waveforms at respective members in time-divisionaldifferential driving;

FIG. 27 is an equivalent circuit diagram of a pixel portion according toa fifth embodiment of the present invention;

FIG. 28 is a sectional view of a stack-type liquid crystal displaypanel;

FIG. 29 is an equivalent circuit diagram of the stack-type liquidcrystal display panel;

FIG. 30 is a sectional view of a stack-type liquid crystal display panelaccording to the fifth embodiment of the present invention;

FIG. 31 is a perspective view showing a plan layout according to thefifth embodiment of the present invention;

FIG. 32 is a perspective view showing another plan layout according tothe fifth embodiment of the present invention;

FIGS. 33-38 show a manufacturing process according to a sixth embodimentof the present invention;

FIG. 39 is a sectional view of a stack-type liquid crystal display panelaccording to an eighth embodiment of the present invention; and

FIG. 40 shows a manufacturing process according to a comparativeexample.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views,embodiments of the present invention are hereinafter described.

FIG. 1 shows a cross-sectional view of a liquid crystal displayaccording to a first embodiment of the present invention.

Three liquid crystal layers LC1-LC3 corresponding to cyan, magenta, andyellow, respectively, are disposed one on another. Three sub-pixelsSP1-SP3 are each interposed between three stacked pixel electrodes P1-P3and an opposed electrode COM to form one pixel. A shield electrode PS isdisposed under the lowest pixel electrode PI with an insulating layerinterposed in between. The shield electrode PS functions as a shieldagainst underlying switching elements (such as thin-film transistors)SW1-SW3 and a wiring line (interconnection) LINE. The switching elementsSW1-SW3 are connected to the respective pixel electrodes P1-P3.

To drive the pixels, first, prescribed potential differences are appliedto the respective sub-pixels SP1 and SP2 via the switching elementsSW1-SW3. Then, a prescribed potential difference is applied to thesub-pixel SP3 that is located between the pixel electrode P3 and theopposed electrode COM in a state that the pixel electrodes PI and P2 arerendered in a floating state by turning off the switching elements SW1and SW2. At this time, a potential is applied to the shield electrode PSsubstantially equal to a potential that is supplied to the pixelelectrode P3. As a result, the potential differences that have beenapplied to the respective sub-pixels SP1 and SP2 are held as they are.That is, in this method, a potential difference is applied to thesub-pixel SP3 after applying potential differences to the sub-pixels SP1and SP2.

There is another method in which potentials are applied to the threepixel electrodes P1-P3 at one time instead of performing two times ofwriting. However, in such a method, it is necessary to apply potentialsto the pixel electrodes P1-P3 after determining, through a calculation,how to allocate potential differences between the potential of theopposed electrode COM and the ground potential. This method requires aperipheral operation circuit and hence is very disadvantageous in termsof manufacturing cost and power consumption.

In contrast, when writing is performed two times as in the presentinvention, no extra calculation is needed, because prescribed potentialdifferences are given to the respective sub-pixels SP1 and SP2 to writesignals thereby supplying potentials to the respective pixel electrodesP1 and P2. Then a potential difference is applied to the sub-pixel SP3(i.e., between the pixel electrode P3 and the opposed electrode COM) byshifting the potentials of the pixel electrodes P1 and P2 while keepingthe potential differences across the respective sub-pixels SP1 and SP2.Therefore, driving can be performed without providing a new peripheraloperation circuit for the liquid crystal display section.

FIGS. 2-5 show cross-sectional views of a liquid crystal display inaccordance with modifications of the first embodiment of the presentinvention. For example, methods for supplying the shield electrode PSwith a potential corresponding to a potential supplied to the pixelelectrode P3 are:

(1) short-circuiting the shield electrode PS and the pixel electrode P3(see FIG. 2);

(2) supplying the shield electrode PS with the same potential assupplied to the pixel electrode P3 via an amplifier (buffer) (see FIG.3);

(3) supplying the shield electrode PS with the same potential assupplied to the pixel electrode P3 from a separate switching element SW4(see FIG. 4); and

(4) supplying the shield electrode PS with the same potential assupplied to the pixel electrode P3 via another capacitance component,(for example, a capacitor having a sufficiently larger capacitance thanthe capacitance of each liquid crystal layer and each auxiliarycapacitor) (see FIG. 5).

The method of FIG. 2 in which the shield electrode PS is short-circuitedwith the pixel electrode P3 is described below.

FIG. 6 shows a circuit configuration of a pixel portion, and FIG. 7 is ablock diagram showing the entire configuration of a display device.

Three liquid crystal layers LC1-LC3 of cyan, magenta, and yellow areprovided for an mth-column/nth-row pixel. Three sub-pixels SP1-SP3 areeach disposed between three pixel electrodes P1-P3 and an opposedelectrode COM. A potential Vcom is applied to the opposed electrode COM.

To determine potentials Vp1-Vp3 of the respective pixel electrodesP1-P3, active elements (in this case, thin-film transistors (TFTs)Tr1-Tr4) are connected to the pixel electrodes P1-P3.

The TFTs Tr1-Tr4 may be formed, for example, of amorphous silicon TFTs,polysilicon TFTs, and crystal silicon TFTs, or may be formed by usingother semiconductor materials.

The drains of the TFTs Tr1 and Tr4 are connected to the respective pixelelectrodes P1 and P2, and the drains of the TFTs Tr2 and Tr3 areconnected to the pixel electrode P3. A signal line Sigml and a scanningline Gnl are connected to the source and the gate, respectively, of theTFT Tr1. A signal line Sigm2 and the scanning line Gnl are connected tothe source and the gate, respectively, of the TFT Tr2. A signal lineSigm3 and a scanning line Gn2 are connected to the source and the gate,respectively, of the TFT Tr3. A line Vc is to be supplied with apotential approximately equal to the center potential of an image signalthat is an AC signal for the liquid crystal and is connected to thesource of the TFT Tr4. The scanning line Gn1 is connected to the gate ofthe TFT Tr4. It is desirable that the active elements and the wiringlines, such as the signal lines and the scanning lines, be formed on asingle substrate.

A pixel shield electrode PSmn is disposed between the pixel electrode P1and at least part of the signal lines Sigmi, the scanning lines Gn1, theactive elements, etc., and electrical connection is thus made so thatthe pixel shield electrode PSmn is given the same potential as the pixelelectrode P3.

The pixel electrodes P1-P3 are provided with respective auxiliarycapacitors Cs1-Cs3 for inhibiting a variation in the potentialdifference across each liquid crystal layer owing to leakage through theliquid crystal layer, or coupling. One electrode of the auxiliarycapacitor Csl for the sub-pixel SP1 is connected to the pixel electrodeP1, and the other electrode is connected to the pixel electrode P3. Oneelectrode of the auxiliary capacitor Cs2 for the sub-pixel SP2 isconnected to the pixel electrode P2, and the other electrode isconnected to the pixel electrode P3. One electrode of the auxiliarycapacitor Cs3 for the sub-pixel SP3 is connected to the pixel electrodeP3, and the other electrode is connected to a line having apredetermined potential (in this case, the line Vc). Although theconnection method of the auxiliary capacitors Cs1-Cs3 depends on thedriving method described below, the electrodes of the auxiliarycapacitor Cs1 may be connected to the respective pixel electrodes P1 andP2. Further, the electrodes of the auxiliary capacitor Cs3 may beconnected to the pixel electrode P3 and a one-line-preceding scanningline, respectively (see FIG. 11). To simplify the layout, the auxiliarycapacitor Cs3 may be connected to the scanning line Gn1.

As shown in FIG. 7, the signal lines Sigmi are connected to a signalline driver circuit and supplied with mth-line image signals for ACdriving of the liquid crystals. The scanning lines Gni are connected toa scanning line driver circuit and supplied with selection-level signalsin order of Gn1 and Gn2. The selection-level signal is a high-levelsignal if the TFTs Tr1-Tr4 are n-channel transistors. The signal linedriver circuit and the scanning line driver circuit are supplied, from acontrol circuit, with control signals, such as a clock signal and astart pulse, for the driver circuits as well as image signals for ACdriving.

FIG. 9 shows signal waveforms according to this embodiment of thepresent invention. The following description is directed to the case ofusing e-channel transistors, and the selection level is assumed to be ahigh level unless otherwise specified. It goes without saying that adevice can be constructed by using p-channel transistors. When thescanning line Gn1 is given a high-level signal, the TFTs Tr1, Tr2, andTr4 are turned on, and hence a signal line potential Vsigml, a wiringline potential Vc, and a signal line potential Vsigm2 are applied to therespective pixel electrodes P1-P3. The potential Vc is set approximatelyequal to a center signal line potential Vsigc. As a result, potentialdifferences VLC1 and VLC2 that are applied to the respective liquidcrystal layers LC1 and LC2 during a period when the potential of thescanning line Gn1 is at a high level are as follows:

VCL 1=Vp 1−Vp 2 =Vsigm 1−Vsigc

VLC 2=Vp 3−Vp 2 =Vsigm 2−Vsigc.

Prescribed potential differences are applied to the sub-pixels SP1 andSP2 in this manner.

Subsequently, the potential of the scanning line Gn1 becomes a lowlevel, and the TFTs Tr1, Tr2, and Tr4 are turned off. Then, thepotential of the scanning line Gn2 becomes a high level, and the TFT Tr3is turned on, whereby the potential of the pixel electrode P3 becomesequal to a signal line potential Vsigm3. Since the TFTs Tr1, Tr2, andTr4 are off, the pixel potentials Vp1 and Vp2 of the respective pixelelectrodes P1 and P2 are in a floating state. When the pixel potentialVp3 changes from the potential immediately before the turning-on of theTFT Tr3 to the signal line potential Vsigm3, a potential variation ΔVp3woccurs that corresponds to the difference between the above twopotentials. A feedthrough voltage ΔVp3 1 occurs in the TFT Tr2 when thepotential of the scanning line Gn1 becomes a low level. Therefore, theabove-mentioned potential immediately before the turning-on of the TFTTr3 is the signal line potential Vsigm2 minus the feedthrough voltageΔVp31.

At this time, since the potential of the shield electrode PSmn is equalto the pixel potential Vp3 and is determined by the TFT Tr3, thecoupling between the pixel electrode P1 and the wiring lines isinhibited. and the potential of the pixel electrode P1 is therebyallowed to vary by approximately ΔVp3w. Since the pixel electrode P2 isinterposed between the pixel electrodes P1 and P3, when the potential ofeach of the pixel electrodes P1 and P3 varies by ΔVp3w, the potential ofthe pixel electrode P2 varies by approximately the same voltage. Whenthe potential of the scanning line Gn2 falls, a feedthrough voltageΔVp32 is added to the pixel potential Vp3. This variation also causesvariations of the pixel potentials Vp1 and Vp2 in the same manner asdescribed above, and hence the potential differences VLC1 and VLC2remain the same as written in the state in which the potential of thescanning line Gn1 was at a high level. Since the pixel potential Vp3 isvaried by a voltage approximately equal to the feedthrough voltageΔVp32, the positive and negative sides of the AC voltage are balancedwith each other by making the opposed electrode potential Vcom lowerthan a center potential Vsigm3c of the signal line potential Vsigm3 byabout ΔVp32.

The signal line driver circuit can be the same as in the conventionalTFT-LCD. FIG. 8 shows an example of a signal line driver circuit thatcan be used in this embodiment of the present invention. The samplingtiming of three sample-and-hold circuits is determined by an output of ashift register, and mth-line signals of CMY image signals are sampled.The signal lines Sigmi are driven via an analog buffer. The signal linedriver circuit may be of other types such as a type in which selectionis made among reference signals and a type in which digital signals arelatched and potentials for signal lines are formed by D/A converters. Inany of those cases, the same signal driver circuit as in theconventional TFT-LCD can be used and the controllability of gradationsignals can be kept high.

Since the scanning line driver drives the two scanning lines Gn1 and Gn2for one pixel, the scanning is performed two times faster than in theconventional case if the operation speed of the signal line driver isthe same as in the conventional case. It is appropriate to add a circuitfor preventing an event so that pulses that are supplied to the scanninglines Gn1 and Gn2 do not become a high level at the same time.

As described above, by providing the shield electrode PSmn, the pixelelectrodes that are rendered in a floating state can be given prescribedpotential variations when signals are written to one pixel that consistsof the sub-pixels SP1-SP3. That is, the coupling between the pixelelectrodes and the signal lines and the scanning lines can be inhibited.An improvement can be made in the phenomenon in which the potentials ofthe pixel electrodes that are rendered in a floating state are hard tovary. As a result, the potential differences across the respectivesub-pixels can be controlled precisely. Hence good images that are freeof crosstalk or the like can be displayed.

FIGS. 10 and 11 schematically show plan layouts of TFT array substratesaccording to this embodiment of the present invention, and FIG. 12 is asectional view including liquid crystal layers (i.e., a sectional viewtaken along line A-A′ in FIGS. 10 or 11).

A manufacturing process etc. is described below.

An array substrate, formed, for example, of a glass substrate, a plasticsubstrate, or a plastic film is prepared. Signal lines, scanning lines,TFTs, and auxiliary capacitors are formed on the array substrate. Aninsulating film-1 made of, for example, a photosensitive acrylic resin,of about 2 μm in thickness is formed on those members, and through-holesfor connection to members to be formed above are formed through theinsulating film-1. Then, after Mo is deposited at a thickness of 200 nmby sputtering, a resist pattern is formed by a photoresist step. A pixelshield electrode PSmn is formed by etching the Mo film, using the resistpattern as a mask. The shield electrode PSmn is connected to a lineleading to a pixel electrode P3. Then, an insulating film-2 made of, forexample, a photosensitive acrylic resin, is applied at a thickness ofabout 2 μm and subjected to pattern formation of through-holes, roughsurface for a reflection electrode, etc. Then, Al, Ag, an Al alloy, orthe like is deposited by sputtering at a thickness of 200 nm andpatterned into a pixel electrode P1. The pixel electrode P1 is alsogiven a function of a reflection electrode. Subsequently, a liquidcrystal layer LC1 is formed by applying guest-host liquid crystals thatare sealed in microcapsules by printing. A transparent pixel electrodeP2 made of an ITO-dispersed resin is formed thereon. Then, a liquidcrystal layer LC2 and a transparent pixel electrode P3 are formedsequentially and a liquid crystal layer LC3 is formed thereon. Then, anopposed substrate provided with an opposed electrode COM is bonded tothe TFT array substrate by a vacuum lamination method, whereby a liquidcrystal panel is completed.

The insulating film-1 and the insulating film-2 may be an organic resinfilm made of, for example, BCB, or a non-photosensitive resin, aninorganic insulating film, such as a silicon oxide film, or a siliconnitride film formed by spin-on-glass, CVD, or sputtering. To reduce thedegree of coupling, it is preferable that the insulating film-1 and theinsulating film-2 have a large degree of thickness. Usually, it isdesirable that their thickness be set at 1-5 μm. However, it is possibleto form an auxiliary capacitor by the pixel electrode P1 and the shieldelectrode PSmn, in which case the insulating film-1 and the insulatingfilm-2 may be given a prescribed thickness (e.g., 200-400 nm) suitablefor such a structure.

Although in the above description microcapsules are used to form eachliquid crystal layer, partitions may be formed by mixing together amonomer and a liquid crystal and polymerizing the monomer by applyinglight or heat. It is also possible to form partitions between liquidcrystal layers by using a thin film (preferably having largepermittivity).

The pixel electrodes may be made of SnOx, InOx-ZnOx, or a conductivetransparent resin instead of containing ITO. Fine particles to bedispersed in a resin may be made of a material other than ITO.

Instead of an absorption-transmission mode guest-host liquid crystal,reflection-transmission mode liquid crystals such as a holographic PDLCand a cholesteric liquid crystal may be used. In the latter case, thepixel electrode P1 and the insulating film-2 may be used as atransparent electrode and a light absorption layer, respectively, or thepixel electrode P1 itself may be made of a light-absorptive materialsuch as a carbon-dispersed resin.

The columnar electrodes for connecting the pixel electrodes to the lowerelectrodes may be formed at the same time as the formation of the pixelelectrodes P2 and P3 by using the same material. The columnar electrodesmay be formed by plating or by forming an electrode on the side face ofa bank of a resin. The columnar electrodes may be formed either beforeor after the formation of liquid crystal layers. When a resin is used,the bank may assume a lattice shape rather than a pole shape.

In this embodiment, as shown in FIGS. 10 and 11, the shield electrodePSmn is disposed under the pixel electrode P1 so as to haveapproximately the same shape as the pixel electrode P1. This allows thepixel electrode P1 to be effectively shielded from the signal lines, thescanning lines, the TFTs, the auxiliary capacitors, etc. that are givenprescribed potentials. The coupling between the pixel electrode P1 andthe shield electrode PSmn can be weakened to a non-problematic level byproperly adjusting the thickness of the insulating film-1, the electrodeareas of the signal lines, and the capacitance of the auxiliarycapacitors. An additional shield electrode that is given a fixedpotential (which may be constant over the entire screen) may be disposedunder the pixel shield electrode PSmn. This prevents variations in pixelpotentials when the signal lines supply signals for other pixels, andhence the deterioration in image quality such as crosstalk can furtherbe reduced.

In the first embodiment described above, the potential of the line forapplying the potential Vc to the pixel electrode P2 can be changed inlink with the opposed electrode potential Vcom instead of being fixed.For example, the potential Vc can be changed approximately in a range ofthe signal amplitude to change the polarity of potential differencesapplied to the liquid crystal layers for every scanning line or everyseveral scanning lines. This measure allows the signal line driver tooutput signals having potential ranges of only one polarity, whereby thebreakdown voltage rating of the signal line driver circuit can bedecreased. In this type of driving. it is preferable to connect theauxiliary capacitor Cs3 of FIG. 6 to the Vc line.

FIGS. 13 and 14 show a modification of the first embodiment of thepresent invention. In this modification, the line for applying thepotential Vc to the pixel electrode P2 that is provided parallel withthe signal lines Sigm1-Sigm3 in FIG. 6 is replaced by a line Csn that isprovided parallel with the scanning lines Gn1 and Gn2. This allows thewiring lines to be formed at wider intervals, thereby contributing toincrease in yield.

There may be provided, between the pixel shield electrode and the wiringlines such as the signal lines, the TFTs, the wiring lines for theauxiliary capacitors Cs, and other members, another shield electrodethat is given a potential (generally a fixed potential) that isindependent of potential variations of those wiring lines. Such anadditional shield electrode may be provided between part of the pixelshield electrode and those wiring lines. This inhibits the phenomenon inwhich the potential of the pixel shield electrode is varied by potentialvariations of those wiring lines, thereby making it possible to providegood image quality with only a low level of crosstalk as caused bypotential variations at the pixel electrodes. This type of additionalshield electrode can also be applied to other embodiments.

Next, a second embodiment of the present invention is described withreference to FIGS. 15 and 16.

In the pixel portion of this embodiment of the present invention, thescanning line for controlling the TFTs Tr1, Tr2, and Tr4 is commonizedwith a scanning line Gn-1 of the preceding stage. This enables theselection time of the scanning line Gn to be two times longer than inthe first embodiment of the present invention.

However, the method of supplying signal line potentials is changed fromthat in the first embodiment of the present invention. That is, when ascanning line Gn-1 for pixels that one-line precede the pixel (m, n) isselected, an image signal for the sub-pixel SP3 of a pixel (m, n-1) issupplied to the signal line Sigm3 and image signals for the sub-pixelsSP1 and SP2 of the pixel (m, n) are supplied to the respective signallines Sigml and Sigm2. In other words, during a period when thepotential of the scanning line Gn-1 is at a high level, signals aresupplied at the same time to the pixel electrode P3 of the pixel (m,h-1) and the pixel electrodes P1 and P2 of the pixel (m, n). This may berealized by providing a line memory for storing an image signal of oneline and delaying part (signal lines Sigml and Sigm2) of image signalsfor the stacked liquid crystal layers by one-line period. The linememory may be provided inside the signal line driver circuit.

FIG. 17 is a block diagram of a circuit in which image signals to besupplied to the signal line driver circuit are delayed by a line memory.The configuration of the liquid crystal panel is as shown in FIGS. 15and 16. The scanning line driver circuit is so configured as to driveone signal line for one pixel. The signal line driver circuit is thesame as shown in FIG. 7.

Turning now to a desciprtion of the structure of sub-pixels, wherein thesub-pixels SP1-SP3 are called subpixels Y (yellow), M (magenta), and C(cyan), respectively. Externally provided image signals are subjected toprescribed conversions in the control circuit, and then a C image signalfor the sub-pixel C is input to the line memory and held there for onescanning period. M and Y image signals are input to the signal linedriver circuit on a real-time basis and a one-scanning-period-precedingimage signal that is stored in the line memory is also input, as a Cimage signal, to the signal line driver circuit. With this measure, Mand Y signals of the nth line are supplied to the respective signallines Sigm1 and Sigm2 during a period in which the potential of thescanning line Gn-1 of the (n-1)th line is at a high level, whereby thesignals are written to the sub-pixels M and Y of the pixel (m, n) viathe respective TFTs Tr1 and Tr2. At the same time, a signal is writtento the sub-pixel C of the pixel (m, n-1) via a TFT Tr3 that is connectedto the pixel (m, n-1).

FIG. 18 shows an example in which a memory function is provided insidethe signal line driver circuit. FIG. 18 shows a portion of the signalline driver circuit that corresponds to pixels of one column. Thesampling timing of two sample-and-hold circuits SHa and SHb isdetermined based on an output of one-bit portion of a shift register.Each of the sample-and-hold circuits SHa and SHb can hold YMC signalsfor pixels of one column. Signals are sampled by one of thesample-and-hold circuits SHa and SHb while a switching control of everyscanning period is performed based on a signal that is supplied from acontrol line. A one-scanning-line-preceding signal can be generated andsupplied to the signal line Sigm3 by supplying outputs of differentsample-and-hold circuits to the signal line Sigm3 for one color and thesignal lines Sigm1 and Sigm2 for the other two colors. A similar conceptmay be used in a D/A converter type configuration.

Features in the layout of an array substrate are further described belowwith reference to FIG. 16. In this embodiment of the present invention,each scanning line can be formed between pixels because the number ofscanning lines Gn is the same as the number of columns of pixels.Therefore, overlapping portions of the pixel electrodes and the scanningline can be eliminated or reduced. As a result, the coupling between thescanning line and the pixel electrode P1 or the pixel shield electrodePSmn can be weakened. Therefore, a feedthrough voltage that is caused bysuch coupling at the time of falls of scanning line pulses can bereduced, and hence potential differences being held no longer decreaseundesirably. As a result, the gate potential ranges for turning off theTFTs can be reduced, which leads to reduction in power consumption.Further, the variation of the feedthrough voltage can be reduced, whichleads to improvement in image quality.

Although in FIG. 16 the auxiliary capacitor Cs3 is formed between thesignal lines Sigm2 and Sigm3, in this embodiment of the presentinvention, it may be formed in the vicinity of the Vc line. This alsoapplies to the first and other embodiments of the present invention.

Next, a third embodiment of the present invention is described withreference to FIGS. 19 and 20. FIG. 20 is a sectional view taken alongline A-A′ in FIG. 19. In this embodiment of the present invention, thepixel shield electrode is provided mainly in an auxiliary capacitorportion that occupies the largest area and would otherwise cause acoupling problem, rather than over the entire pixel. One terminal ofeach of a first auxiliary capacitor Csl and a second auxiliary capacitorCs2 are connected to a first electrode and a second electrode of apixel. The other terminals of the auxiliary capacitor Cs1 and Cs2 areconnected to an upper electrode of a third auxiliary capacitor Cs3.

An example of a manufacturing process according to this embodiment ofthe present invention is described below in which inverted staggeredstructure amorphous silicon TFTs are used.

MoW, Al, an Al alloy, or the like is deposited on a glass substrate or aplastic substrate at a thickness of 100-500 nm by sputtering, and thenpatterned into a scanning line and gate electrodes of TFTs. At the sametime, a Cs line, a bottom electrode-1 of an auxiliary capacitor Cs1, abottom electrode-2 of an auxiliary capacitor Cs2, a bottom electrode-3of an auxiliary capacitor Cs3, and wiring lines to cross a signal lineSigm2 are formed by the same patterning step, using the same materialwhich formed the scanning line.

Subsequently, an insulating film a as a gate insulating film made ofSiNx or SiNx/SiOx (lamination) is formed at a thickness of about 100-500nm. An amorphous silicon film of about 20-1200 nm in thickness is formedthereon. A SiNx film of about 100-500 nm in thickness is formed on theamorphous silicon film. After upper insulating films are sequentiallyformed in this manner by plasma CVD or the like and patterned by backexposure, an n+ semiconductor layer is formed by plasma CVD or the like.After the n+ semiconductor layer is patterned properly, through-holesfor connection to the bottom electrodes are formed. Thereafter,electrodes to serve as sources, drains, and signal lines are formed bydepositing a conductive material such as Mo, Mo/A1 (lamination), or ITOby sputtering or the like and then patterning it. At the same time, atop electrode-1, 2, and 3 of the respective auxiliary capacitors Cs1-Cs3are formed.

Subsequently, after the portions of the n+ semiconductor layer on thechannels are etched out, an insulating film c as a passivationinsulating film made of SiNx or the like is formed. Then, an insulatingfilm b as an interlayer insulating film that is an organic insulatingfilm made of a photosensitive acrylic resin, BCB, or the like is formedat a thickness of about 1-10 μm so as to have proper contact holes. Apixel electrode P1, a liquid crystal layer LC1, a pixel electrode P2, aliquid crystal layer LC2, a pixel electrode P3, and a liquid crystallayer LC3 are sequentially formed on the insulating film b, and anopposed substrate that is formed with an opposed electrode is placedthereon, whereby a liquid crystal panel is completed.

The TFTs may also be polysilicon TFTs or the like. Although in such acase a different manufacturing process is employed as exemplified byexecution of excimer laser annealing and the TFT structure is changed(e.g., the planar structure is employed), the manners of electrodeformation and insulating film formation can be changed in accordancewith those differences.

The areas of the auxiliary capacitors Csi are increased to increasetheir capacitance. However, increasing the areas of the auxiliarycapacitors Csi leads to an increase in the coupling with the pixelelectrodes. In view of this, as shown in FIGS. 19 and 20 the topelectrode-3 is formed so as to be given the same potential as the pixelelectrode P3, whereby the Cs line having a large area which is to begiven a fixed potential can be shielded from the pixel electrode P1.That is, the top electrode-3 has a function equivalent to the functionof the pixel shield electrode.

The driver circuits may have similar configurations to theconfigurations of the driver circuits of the second embodiment of thepresent invention. Although the coupling between the pixel electrode P1and the signal lines is not zero, it can be weakened to a level that issubstantially non-problematic by thickening the interlayer insulatingfilm, decreasing the wiring line widths, and increasing the capacitanceof the auxiliary capacitors. In particular, it is preferable to applythis embodiment of the present invention to a device in which the numberof gradation levels is small.

FIG. 21 is a schematic circuit diagram showing the coupling weakeningeffect of the present invention.

C1-C3 represent capacitances of the respective sub-pixels to each ofwhich a liquid crystal layer and an auxiliary capacitor contribute, andCst represents a parasitic capacitance formed by the pixel electrode P1and the wiring lines. In the case of the driving method of the firstembodiment of the present invention. potential variations ΔVp13w andΔVp23w at the respective pixel electrodes P1 and P2 that occur when thepotential Vp3 is given a variation ΔVp3w (Vsigm3−Vsigm2) are given by

ΔVp 13 w=ΔVp 3 w(C 1·C 2+C 2·Cst)/(C 1 ·C 2+C 1·Cst+C 2·Cst)

 ΔVp 23 w=ΔVp 3 w(C 1·C 2)/(C 1·C 2+C 1·Cst+C 2·Cst).

If it is assumed that C1=C2=C and Cst=αC, the above equations aremodified as follows:

ΔVp 13 w=ΔVp 3 w(1+α)/(1+2α)

ΔVp 23 w=ΔVp 3 w/(1+2αa).

The maximum value of ΔVp3w is equal to Vsigmax, which is about 5V.Therefore, to make the variations ΔVp13w and ΔVp23w 10 mV or less, α is0.001 or less. With assumptions that the relative permittivity and thethickness of each liquid crystal layer are 5 and about 5 μm,respectively, and the pixel area is about 90% of a square area havingsides of about 150 μm, each liquid crystal layer has a capacitance Clcof about 0.18 pF. If the signal line width is about 5 μm and theinsulating film b is an organic film having relative permittivity of 3and a thickness of about 2 μm, Cst is equal to 9.5×10-15 F. Therefore,the ratio of Cst to Clc is 0.053, which is 53 times larger than thetarget value of α. If auxiliary capacitors are provided so that each ofC1-C3 becomes one-order larger than Clc, the variations can be reducedto 50 mV, which is five times the above-mentioned target value. It canbe said that even this value is allowable because gradation inversiondoes not occur as long as the number of gradation levels is small.

FIG. 22 shows the basic configuration according to a fourth embodimentof the present invention.

Three liquid crystal layers LC1-LC3 corresponding to cyan, magenta, andyellow are disposed one on another. Three sub-pixels SP1-SP3 are eachinterposed between three stacked pixel electrodes P1-P3 and a shieldelectrode PS, whereby one pixel is formed. The shield electrode PS isdisposed under the lowest pixel electrode P1. The shield electrode PSfunctions as a shield against underlying switching elements (thin-filmtransistors or the like) SW1-SW3 and a wiring LINE. The switchingelements SW1-SW3 are connected to the respective pixel electrodes P1-P3.

To drive the pixels, prescribed potential differences are first appliedto the respective sub-pixels SP2 and SP3 via the switching elementsSW1-SW3. Then, a prescribed potential difference is applied to thesub-pixel SP1 in a state in which the pixel electrodes P2 and P3 havebeen rendered in a floating state by turning off the switching elementsSW2 and SW3. At this time, the shield electrode PS is given a commonpotential, for example. As a result, the potential differences that havebeen applied to the respective sub-pixels SP2 and SP3 are held as theyare.

FIG. 23 shows one pixel portion according to this embodiment of thepresent invention. First, to drive the sub-pixels SP2 and SP3, a commonpotential is supplied from the Vc line to the pixel electrode P2 and, atthe same time, prescribed signal potentials are supplied from the signalline Sigm2 and Sigm3 to the pixel electrodes P1 and P3 via the TFTs Tr2and Tr4. Subsequently, the pixel electrodes P2 and P3 are rendered in afloating state and, at the same time, the common potential is suppliedfrom the Vc line to the shield electrode PSmn (also functions as a pixelelectrode) and a prescribed signal potential is supplied from the signalline Sigm1 to the pixel electrode P1. At this time, because of thepresence of the shield electrode PSmn which covers most of the pixel,the states of the sub-pixels SP2 and SP3 can vary from the states inwhich they hold the potentials applied thereto. In this embodiment ofthe present invention, the shield electrodes PSmn of all pixels areintegrated to become a common electrode.

FIG. 24 shows another example of a pixel portion according to thisembodiment of the present invention. First, to drive the sub-pixels SP2and SP3, a common potential Vc is supplied to the pixel electrode P2and, at the same time, prescribed signal potentials are supplied fromthe signal lines Sigm2 and Sigm3 to the pixel electrodes P1 and P3 viathe TFTs Tr2 and Tr4. Subsequently, the pixel electrodes P2 and P3 arerendered in a floating state and, at the same time, a prescribed signalpotential is supplied from the signal line Sigm1 to the shield electrodePSmn and the common potential is supplied from the Vc line to the pixelelectrode P1. The shield electrode PSmn also functions as a pixelelectrode. At this time, because of the presence of the shield electrodePSmn which covers most of the pixel, the states of the sub-pixels SP2and SP3 can vary from the states in which they hold the potentialsapplied thereto.

Although in the examples of FIGS. 23 and 24 each of the auxiliarycapacitors Cs1-Cs3 is provided between adjacent pixel electrodes, thepixel electrodes P1-P3 may form capacitors with the shield electrodePSmn so as to include parasitic capacitances. Although in the examplesof FIGS. 23 and 24 driving is performed by using two scanning lines forone pixel as in the case of FIG. 6, they can also be applied to thedriving in which only one scanning line is used for one pixel as in thecase of FIG. 16.

It is possible to cause the shield electrode to function as a reflectionplate by forming asperity on its surface. Further, an alternativestructure is possible in which a transparent shield electrode is usedand a reflection surface, a holographic reflection surface, a whitepaint surface, or the like is provided under the shield electrode.

Although the first to fourth embodiments of the present invention aredirected to the case of using three liquid crystal layers, theabove-described concepts can also be applied to the case of using fourliquid crystal layers (CMY plus black and white) or even five or moreliquid crystal layers. In the case of using four liquid crystal layers,a configuration corresponding to the first embodiment of the presentinvention, for example, is such that an additional, fourth pixelelectrode and a fourth liquid crystal layer are disposed under theopposed electrode to form an additional sub-pixel. Prescribed potentialdifferences are given to the respective sub-pixels by supplyingpotentials to the first to fourth pixel electrodes. Thereafter, thefirst to third pixel electrodes are rendered in a floating state and thesame potential is supplied to the fourth pixel electrode and the shieldelectrode, and then a prescribed potential difference is applied to thefourth sub-pixel.

Writing to the pixel electrodes may be performed separately for eachsub-pixel in a time-divisional manner. For example, a configurationcorresponding to the first embodiment may be such that the potential ofthe sub-pixel SP2 is determined after determination of the potential ofthe sub-pixel SP1 and the potential of the sub-pixel SP3 is determinedlast.

The shield electrode is preferably fixed to the same potential as thesecond electrode when the sub-pixel SP1 is floating and the sub-pixelSP2 is impressed a signal, and the shield electrode is fixed to the samepotential as the third electrode when the sub-pixel SP3 is impressed asignal. In fact, the shield electrode and the third electrode areimpressed the same potential as the second electrode at impressing asignal to the sub-pixel SP1. Since the potentials of the third electrodeand the second electrode changes similarly at impressing a signal to thesub-pixel 2, the first electrode can change with the shield electrodeeasily.

Next, a fifth embodiment of the present invention is described. Beforemaking a specific description of the fifth embodiment of the presentinvention, a description is made of problems that occur when atime-divisional differential driving technique is applied to areflection/stack-type liquid crystal display panel produced by aconventional manufacturing technique, as well as methods for solvingthose problems.

First, a problem associated with the juxtaposition of auxiliarycapacitor electrodes and a method for solving it is described.

FIG. 25 shows an example of an equivalent circuit of one pixel of athree-layer-stacked liquid crystal display panel that is subjected totime-divisional differential driving. In FIG. 25, LC1-LC3 denote liquidcrystal layers, SW1-SW3 denote driving elements, G1-G3 denote gatesignal lines, and S1-S3 denote image signal lines. COM denotes anopposed electrode, and J1-J3 denote the voltage supply points of thedriving element.

The time-divisional differential driving is performed according to atiming chart shown in FIG. 26. First, in period T1, the potentials ofthe gate signal lines G1 and G2 are set at a H state, whereby thedriving elements SW1 and SW2 are turned on. In this period, a pixelpotential for LC1 is given to the image signal line S1. In the followingdescription, the pixel potential for LC1 means a potential that deviatesfrom a signal reference potential Vsig-c by an image potential Vsigl. Aprescribed potential difference is applied to the liquid crystal layerLC 1 by setting the potential of the image signal line S2 at a commonpotential. In the following description, the common potential means apotential that is deviated from the signal reference potential Vsig-c byan opposed electrode potential Vcom.

After a lapse of period T1, the potential of only the gate signal lineG1 is returned to a L state, whereby the driving element SW1 is turnedoff and the liquid crystal layer LC1 is rendered in a floating state. Inthis state, the potential difference across the liquid crystal layer LC1is held even if the potential on the driving element SW2 side varies. Inperiod T2 which starts immediately after period T1, the potential of thegate signal line G3, in addition to the potential of the gate signalline G2, is set at a H state, whereby the driving elements SW2 and SW3are turned on. In this period, a prescribed potential difference isgiven to the liquid crystal layer LC2 by switching the potential of theimage signal line S2 to a pixel potential for LC2 and setting thepotential of the image signal line S3 at the common potential.

After a lapse of period T2, the potential of the gate signal line G2 isreturned to a L state, whereby the liquid crystal layer LC2 is alsorendered in a floating state. As a result, the potential differencesacross the respective liquid crystal layers LC1 and LC2 are maintained.In period T3 which starts immediately after period T2, the potential ofthe image signal line S3 is switched to a pixel potential for LC3 whilethe potential of the gate signal line G3 is kept at the H state, wherebya prescribed potential difference is given to the liquid crystal layerLC3 (i.e., between the image signal line S3 and the opposed electrode).After a lapse of period T3, the potential of the gate signal line G3 isreturned to a L state, whereby potential setting of one pixel iscompleted.

Although in FIG. 26 the waveforms of the signals for S1-S3 are such thatthe polarity with respect to the reference potential is inverted foradjacent layers, selection can be made from various kinds of polarityrelationships between the layers.

In the above driving method, to provide auxiliary capacitors forcompensating for the potential difference holding characteristic of theliquid crystal layers, the auxiliary capacitors CS1-CS3 are provided inseries with each other and in parallel with the corresponding liquidcrystal layers LC1-LC3, respectively, as shown in FIG. 27.

On the other hand, in the three-layer-stacked reflection-type liquidcrystal display panel, it is desirable that the driving elements and thesignal lines be formed together right under the reflection electrode.This is to secure a sufficient display area and reduce the manufacturingcost. In this case, to apply drive voltages to the respective liquidcrystal layers, vertical conductors are provided beside each pixelregion as shown in FIG. 28.

A manufacturing process for the conventional configuration is asfollows. First, image signal lines, voltage supply pads for verticalconductors, and auxiliary capacitor electrodes connected to those padsare patterned in the same plane by a single process. Then, capacitorsare formed by the above electrodes and electrodes which are patterned asan extension of gate or signal lines. FIG. 29 is an equivalent circuitdiagram of this configuration and is different from the equivalentcircuit diagram of FIG. 27. In this circuit configuration, the liquidcrystal layers LC1 and LC2 are never rendered in a floating state. Inthe configuration of FIG. 29, the potential of an auxiliary capacitoropposed electrode CS-COM is the same as that for one of the above gateor signal lines. However, the above situation remains the same even ifauxiliary capacitor opposed electrodes for the respective layers areformed independently of each other, unless they are disconnected toabove gate or signal lines. That is, there is a problem thattime-divisional differential driving cannot be realized by a structurein which auxiliary capacitor electrodes are simply juxtaposed with eachother.

To solve the above problem, this embodiment of the present inventionemploys a structure in which auxiliary capacitor electrodes are laid oneon another. In the manufacture of this structure, the number of stepsfor patterning auxiliary capacitor electrodes is increased from thenumber in the conventional manufacturing method. The increase in thenumber of steps can be minimized by laminating only two electrodes thatare to be connected to the SW2 voltage supply point (J2 in FIG. 27) andthe SW3 voltage supply point (J3 in FIG. 27) when the associatedelectrodes are rendered in a floating state. In this case, the otherelectrode for forming the auxiliary capacitor CS1 also serves as adisplay electrode (reflective electrode) of the liquid crystal layerLC1. However, in many cases, asperity is formed on an electrode forcontrolling the reflective characteristic. In such a case, a spatialvariation of the interelectrode distance makes it difficult to determinethe capacitance value. Therefore, it is desirable to form also theauxiliary capacitor CSl separately. FIG. 30 is a sectional view showingsuch a configuration conceptually. Eventually, the equivalent circuit ofFIG. 27 can be realized with the minimum number of additional steps whenthe auxiliary capacitor electrodes are disposed in the order that isopposite to the stack order of the corresponding pixel electrodes.

Next, a problem associated with the in-plane layout of auxiliarycapacitors and a method for solving it is described.

Usually, from the viewpoint of the voltage holding function, that is,from the viewpoint of securing sufficiently large auxiliary capacitancevalues, it is sufficient to form auxiliary capacitor electrodes only inregions right under parts of a reflective electrode. However, in thisstructure, non-negligible capacitances are caused by the reflectiveelectrode and conductors (signal lines, electrodes, vertical conductors)provided right under the reflective electrode. Those capacitances causesthe potential of the reflective electrode to be varied throughcapacitive coupling at every potential variation during scanningperiods. In particular, because the potentials of the signal lines areswitched plural times for one pixel, the rate of occurrence of potentialvariations is higher in time-divisional differential driving than in theconventional driving.

In the present invention, to inhibit potential variations, the auxiliarycapacitor electrodes are made as wide as possible. In this case, becauseof the potential shield effect of a planar electrode, the couplingbetween electrodes above and below each auxiliary capacitor electrodebecomes very small. In particular, it is effective to dispose theelectrode connected to the J1 point between the reflective electrode andthe electrode connected to the J2 point with an intention to obtain apure shield effect. It is preferable to increase the stacked electrodearea in order of the electrode connected to the J3 point, the electrodeconnected to the J2 point, and the electrode connected to the J1 point.Alternatively, the stacked electrode area may be increased in order ofthe electrode connected to the J3 point, the electrode connected to theJ2 point, and the reflective electrode. It is also desirable to employ aplan layout in which related wiring lines are covered with eachauxiliary capacitor electrode as much as possible. Even if the electrodeareas are made different so as to have a particular ratio, arbitrarycapacitance values can be obtained by adjusting the electrode intervalor the relative permittivity of an insulating layer provided between theelectrodes.

If the efficiency of covering of wiring lines by the auxiliary capacitorelectrodes is taken into consideration, that is, if the fact that alower auxiliary capacitor electrode can cover a smaller number of signalelectrodes is taken into consideration, it is desirable to form theimage signal line S3 for the highest liquid crystal layer inside and theimage signal lines S1 and S2 for lower liquid crystal layers outside.FIG. 31 is a perspective view showing an example plan layout ofauxiliary capacitor electrodes and signal lines that satisfies the aboveconditions. Electrodes that are disposed right above driving elements atthe same height as image signal lines are dotted in FIG. 31. CSE1-CSE3denote auxiliary capacitor electrodes. The auxiliary capacitor electrodeCSE1 may also serve as a reflective pixel electrode for the lowest LClayer. However, when the bottom surface of a reflective electrode isformed with asperity (e.g., it is embossed), it is desirable to providea reflective pixel electrode for the lowest LC layer separately from theauxiliary capacitor electrode CSE1. An electrode opposed to auxiliarycapacitor, which is disposed at the same height as or below gate lines,is omitted in FIG. 31. PAD1-PAD3 denote voltage supply pads forconnection to vertical conductors. If the voltage supply pads PAD1-PAD3are disposed in the vicinity of driving element voltage supply portions,the loss of voltage supply to pixel electrodes located above is madesmall.

If a layout in which the gate line G1 for the lowest liquid crystallayer is disposed inside and the gate lines G2 and G3 for higher liquidcrystal layers are disposed outside is combined with time-divisionaldifferential driving, the gate line for the lowest layer can also serveas an auxiliary capacitor opposed electrode. This is because waveformscan be set so that the H-state period for the lowest layer does notoverlap with the H-state period for the highest layer as shown in FIG.26. This structure further simplifies the configurations of peripheralcircuits. FIG. 32 is a perspective view showing an example plan layoutof auxiliary capacitor electrodes and gate lines for the two lowerlayers that satisfy the above conditions. An auxiliary capacitor opposedelectrode CS-COM that is located at the same height as the gate lines isdotted in FIG. 32.

Examples of the material for forming the auxiliary capacitor electrodesthat can be used in this embodiment of the present invention are metalssuch as Al, Mo, Cr, Ta, and W and alloys that are combinations of thosemetals. If it is intended to give the auxiliary capacitor electrode CSE1only a function of electrical shielding against influences from lowersurfaces, it may also be made of an organic conductive material.

It is desirable that the interlayer insulating layer that constitutesthe auxiliary capacitors be made of a material that provides a goodcontact with the driving elements. In particular, when the drivingelements are Si transistors, a nitride (SiNx) and an oxide (SiOx) aregenerally used for this purpose. When a higher level of dielectricperformance (that is an electric field concentration effect) isrequired, an oxide of Ta or Ti is used. When a low level of dielectricperformance (that is, an electric field shield effect) is required,organic materials are used.

Examples of the liquid crystal material are liquid crystals with phenylfluoride group, cyano biphenyl liquid crystals, and liquid crystals withester bond. Since display is performed in a mode in which light isabsorbed when no potential is applied, dielectric anisotropy aredesirable.

Examples of the dichroic dye molecule are yellow dyes having thefollowing chemical formulae (1)-(9), magenta dyes having the followingchemical formulae (10)-(17), and cyan dyes having the following chemicalformulae (18)-(21):

The concentration of the dichroic dye to the liquid crystal material is0.01-10%, preferably 0.1-5%. If the concentration is too small, thecontrast is not sufficiently high. If the concentration is too large,coloration remains even during potential application, and hence thecontrast ratio is not sufficiently high either.

Examples of the binder resin are thermoplastic resins including ethylenepolymers; ethylene chloride polymers; ethylene copolymers such as anethylene-vinyl acetate copolymer and an ethyl acrylate maleic anhydridecopolymer; butadiene polymers; polyesters such as polyethyleneterephthalate, polybutylene terephthalate, and polyethylene naphthalate;propylene polymers; isobutylene polymers; vinyl chloride polymers;vinylidene chloride polymers; vinyl acetate polymers; vinyl alcoholpolymers; vinyl acetal polymers; vinyl butyral polymers; homopolymer oftetrafluoroethylene; homopolymer of trifluoroethylene; fluoroethylenepropylene copolymers; vinylidene fluoride polymers; vinyl fluoridepolymers; tetrafluoroethylene copolymers such as perfluoroalkoxytetrafluoroethylene copolymers, or tetrafluoroethylene perfluorovinylether copolymers, a tetrafluoroethylene hexafluoropropylene copolymer,and tetrafluoroethylene copolymers; fluorinated polymers such asfluorinated polybenzoxazole and fluororinated polybenzothiazoles;acrylic acid polymers; methacrylic acid polymers such as polymethylmethacrylate; acrylonitrile polymers; acrylonitrile copolymers such asan acrylonitrile-butadiene-stylene copolymers; stylene polymers; stylenehalogenide polymers; stylene copolymers such as a stylene-methacrylicacid copolymers and a stylene-acrylonitrile copolymers; ionic polymerssuch as sodium polystylenesulfonate and sodium polyacrylate; acetalpolymers; polyamides such as nylon 66; gelatins; industrial gums;polycarbonates; ester-carbonate copolymers; cellulose polymers; phenolicpolymers; polyureas; epoxy polymers; unsaturated polyesters; alkydpolymers; melamine copolymers; polyurethanes; diaryl phthalate polymers;polyphenylene ethers; polyphenylene sulfides; polysulfones; polyphenylsulfones; silicone polymers; polyimides; bismaleimide triazine polymers;polyimideamides; polyethersulfones; 4-methyl-1-pentene polymers;polyetheretherketones; polyetherimides; polyvinyl carbazoles; andnorbornene-type amorphous polyolefins.

Examples of the liquid crystal encapsulation technique are aninterracial polymerization method, an in-situ polymerization method, acoacervation method, a method with phase separation from an aqueous oran organic solution system, a method with devolatilization from anemulsion, Wurster air suspension method, and a spray drying method.Selection can be made properly from those methods in accordance with thedisplay mode, or shape, of a liquid crystal display device. Examples ofthe capsule are thermosetting resins including condensation polymerssuch as melamine polymers, epoxy polymers, urea polymers, phenolicpolymers, and furan polymers, and three-dimensional cross-linking vinylpolymers such as stylene-divinylbenzene copolymers and methylmethacrylate-vinyl acrylate copolymers; and the thermoplastic resinsthat have been disclosed above as the examples of the binder resin.Further, liquid crystal may be encapsulated by forming a multi-layercapsule by using two or more resins that are selected from the abovethermosetting resins and thermoplastic resins. In this case, to improvethe heat stability of microcapsules, it is preferable to use athermosetting resin as the outermost layer.

Next, a sixth embodiment of the present invention is described.

An anthraquinone-type yellow dichroic dye having the followingstructural formula (22) was dissolved in a liquid crystal mixtureLixon-5035XX (product name; produced by Chisso Corporation).

Monomers, that is, a methyl methacrylate monomer of 3 wt % and anoctadecyl methacrylate monomer of 12 wt %, and divinylbenzene of 1 wt %as a crosslinking agent were mixed into and dissolved in the aboveliquid crystal mixture of 84 wt %. By using an emulsification apparatus(produced by Ise Chemicals Corp.), an emulsion was obtained by causing aresulting mixed liquid to pass through a hydrophilic porous glass tubehaving an average hole diameter of 1 μm and squeezing it out of the tubeinto a flow of a 0.3 wt % aqueous solution of polyvinyl alcohol byapplying hydrostatic pressure of 1.5 atm to the liquid. The emulsionthat is a liquid crystal composition was polymerized at 85° C. for 1hour while being stirred at 50 rpm, and then refined by causing it topass through, together with pure water, a porous tube that is made of anion-exchangable resin. The shape of resulting encapsulated liquidcrystal containing the yellow dye was observed with a opticalmicroscope; they were spherical and had an average diameter of 6 μm.

Encapsulated liquid crystal containing a magenta dye was produced by asimilar process, using an anthraquinone-type magenta dichroic dye havingthe following structural formula (23):

Encapsulated liquid crystal containing a cyan dye was produced by asimilar process, using an anthraquinone-type cyan dichroic dye havingthe following structural formula (24):

A Mo-Ta alloy was deposited, at a thickness of about 250 nm, on a glasssubstrate of about 0.7 mm in thickness and then patterned to form gateelectrodes (three systems for one pixel) and an electrode opposed toauxiliary capacitor in a layout shown in FIG. 33.

After a gate insulating layer was formed by depositing SiOx at athickness of about 300 nm and SiNx at a thickness of about 50 nm, a-Si(for a channel layer) and SiNx (for a channel protective layer) weredeposited consecutively at respective thicknesses of about 50 nm andabout 200 nm. After the channel protective layer was etched intoisland-like shapes, an ohmic contact layer was formed by depositingn+a-Si at a thickness of about 50 nm and then the a-Si layer and then+a-Si layer were etched into island-like shapes, whereby channels(three systems for one pixel) were formed at positions shown in FIG. 34.Then, gate electrode lead-out portions of the gate insulating layer wereremoved.

Subsequently, Cr and Al were deposited at respective thicknesses ofabout 50 nm and about 300 nm and then patterned, whereby drainelectrodes connected to respective three-system signal electrodes wereformed on one side of the respective channels. A first-system connectionpad electrode connected to a first-system source electrode was formed onthe other side of the first-system channel. A second-system connectionpad electrode connected to a second-system source electrode was formedon the other side of the second-system channel. A third-system verticalconductor connection pad electrode connected to a third-system sourceelectrode was formed on the other side of the third-system channel. Athird-system auxiliary capacitor electrode was also formed (see FIG.35).

The portions of the n+a-Si layer between the source and drain electrodeswere removed by etching selectively with respect to the channelprotective layer with the signal electrodes used as masks. After SiNxwas deposited at a thickness of about 300 nm, the portions of the SiNxfilm above the first and second-system connection pad electrodes, thethird-system vertical conductor connection pad electrode, end padelectrodes of matrix electrodes, and the source electrodes were removedby etching. Thereafter, Mo was deposited at a thickness of about 300 nmand then patterned, whereby a second-system vertical conductorconnection pad electrode and a second-system auxiliary capacitorelectrode were formed so as to be connected to the second-systemconnection pad electrode (see FIG. 36).

Then, after SiNx was deposited at a thickness of about 400 nm, theportions of the SiNx film on the first-system connection pad electrode,the second and third-system vertical conductor connection padelectrodes, the end pad electrodes of the matrix electrodes, and thesource electrodes were removed by etching. Further, Mo was deposited ata thickness of about 300 nm and then patterned, whereby a first-systemvertical conductor connection pad electrode and a first-system auxiliarycapacitor electrode were formed so as to be connected to thefirst-system connection pad electrode (see FIG. 37).

Thereafter, SiNx was deposited at a thickness of about 200 nm, and itsportions on the first to third-system vertical conductor connection padelectrodes, the peripheral pad electrodes, and the source electrodeswere removed by etching. An undercoat layer for reflective electrode wasformed by coating polyimide on the SiNx layer at a thickness of about 1μm, and its portions on the first to third-system vertical conductorconnection pad electrodes were removed by etching. After the surface ofthe polyimide film was subjected to dimple formation by mold thrusting,Al was deposited at a thickness of about 200 nm and patterned into areflective pixel electrode.

Then, the first-system vertical conductor connection pad electrode wasconnected to the reflective pixel electrode with a hydrophobicconductive paste. At the same time, a first electrode pole of about 10μm in height and a second electrode pole of about 22 μm in height wereformed on the second and third-system vertical conductor connection padelectrodes, respectively.

A yellow light modulation layer was formed by coating the encapsulatedliquid crystal containing yellow dye and binder resins to the abovestructure by screen printing.

The above second-layer film was coated with a protective film that is anaqueous solution of hydroxymethylethyl cellulose, which had affinity forthe encapsulated liquid crystal film but had no affinity for theelectrode poles. The aqueous solution was dried at about 120° C., whichis lower than the glass transition temperature of the capsule material.It is preferable that the contact angle between the protective film andthe encapsulated liquid crystal film be smaller than 5° and that thecontact angle between the protective film and the electrode poles belarger than 50°.

Then, all the laminated films were subjected to annealing in an airatmosphere, whereby the surface of the protective film was renderedhydrophobic and the adhesion between the liquid crystal microcapsulesand the substrate was increased. A toluene solution of polyester, forexample, as a hydrophobic ITO filler dispersion liquid, which hadaffinity for both of the protective film and the electrode poles, wasapplied to the above structure selectively, that is, in electrodeshapes. The solution was dried at ordinary temperature in a nitrogenatmosphere, and then illuminated with ultraviolet light having a centerwavelength 147 nm to both set it and render it conductive. As a result,electrical connection between a resulting film and the top portion ofthe first electrode pole was secured.

Subsequently, steps similar to the above were performed, whereby a cyanlight modulation layer that was constituted of encapsulated liquidcrystal containing a cyan dye, and a protective film were formedsequentially. Annealing was then performed in an air atmosphere, wherebythe entire surface of the protective film was rendered hydrophobic andthe adhesion between the liquid crystal microcapsules and the substratewas increased. A toluene solution of polyester, for example, as ahydrophobic ITO filler dispersion liquid, which had affinity for both ofthe protective film and the electrode poles, was applied to the abovestructure selectively, that is, in electrode shapes. The solution wasdried at ordinary temperature in a nitrogen atmosphere, and thenilluminated with ultraviolet light having a center wavelength 147 nm toboth set it and render it conductive. As a result, electrical connectionbetween a resulting film and the top portion of the second electrodepole was secured.

Subsequently, a magenta light modulation layer that is constituted ofencapsulated liquid crystal containing a magenta dye, and a protectivefilm were formed sequentially by similar steps. Finally, a glasssubstrate formed with a transparent electrode was heated andpressure-bonded to the top portion of the above structure, whereby athree-layer stack-type liquid crystal display panel having a sectionalstructure as shown in FIG. 30 was obtained.

When pixel portions of this liquid crystal display panel was observedwith a microscope, capsules were not damaged at all and liquid crystalmolecules were aligned approximately parallel to the substrate with noalignment defects. Having no intermediate substrates, this liquidcrystal display panel was free of parallax due to a stack structure.When driver ICs were mounted by TAB and AC voltages having a maximumsignal amplitude 5 V were applied between the three layers independentlyaccording to the timing chart shown in FIG. 26, 6-bit color display witha monochromatic contrast ratio of 5:1 and good hue performance wasobtained.

In a seventh embodiment of the present invention, spherical liquidcrystal microcapsules having an average diameter of about 6 μm andcontaining a yellow, magenta, or cyan dye are produced by the samemethod as in the sixth embodiment of the present invention.

A Mo—Ta alloy is deposited, at a thickness of about 250 nm, on a glasssubstrate of about 0.7 mm in thickness and then patterned, whereby gateelectrodes are formed in three systems for one pixel. At this time, thefirst-system gate electrode is shaped like the lower layer in FIG. 32because it is to also serve as an auxiliary capacitor opposed electrode.

A three-layer stack-type liquid crystal display panel having the samesectional structure as in the sixth embodiment of the present inventionexcept that the wiring shapes of the two layers immediately above theglass substrate are as shown in FIG. 32 is produced by the samemanufacturing process as in the sixth embodiment of the presentinvention.

When driver ICs were mounted by TAB, and AC voltages having a maximumsignal amplitude 5 V were applied between the three layers independentlyaccording to the timing chart shown in FIG. 26, 6-bit color display witha monochromatic contrast ratio of 5:1 and good hue performance wasobtained.

Next, an eighth embodiment of the present invention is described.

TFTs of three systems for one pixel and wiring lines therefor are formedin the same manner as in the above.

An undercoat layer for reflective electrode is formed by coatingpolyimide on the above structure at a thickness of about 1 μm, and itsportions on the first to third-system vertical conductor connection padelectrodes are removed by etching. After the surface of the polyimidefilm is subjected to dimple formation by mold thrusting, Al is depositedat a thickness of about 200 nm and patterned into a reflective opposedelectrode.

A first electrode pole of about 34 μm in height, a second electrode poleof about 22 μm in height, and a third electrode pole of about 10 μm inheight are formed on the first to third-system vertical conductorconnection pad electrodes, respectively.

A yellow light modulation layer that is constituted of liquid crystalmicrocapsules containing a yellow dye is formed on the above structureand its electrical connection to the top portion of the third electrodepole is secured by the same steps as in the sixth embodiment. Similarly,a cyan light modulation layer that is constituted of liquid crystalmicrocapsules containing a cyan dye is formed and its electricalconnection to the top portion of the second electrode pole is secured.Similarly, a magenta light modulation layer that is constituted ofliquid crystal microcapsules containing a magenta dye is formed and itselectrical connection to the top portion of the first electrode pole issecured.

A glass substrate is heated and pressure-bonded to the top portion ofthe above structure, whereby a three-layer stack-type liquid crystaldisplay panel having a sectional structure as shown in FIG. 38 isobtained. Driver ICs are mounted by TAB. When AC voltages having amaximum signal amplitude 5 V were applied between the three layersindependently according to the timing chart shown in FIG. 26, 6-bitcolor display with a monochromatic contrast ratio of 5:1 and good hueperformance was obtained

COMPARATIVE EXAMPLE 1

Spherical liquid crystal microcapsules having an average diameter ofabout 6 μm and containing a yellow, magenta, or cyan dye were producedby the same method as in the sixth embodiment of the present invention.A lower substrate having driving elements of three systems was producedin the following manner.

The steps to the three-system channels forming step and the subsequentgate insulating layer removing step were the same as in the sixthembodiment of the present invention. However, a plan layout shown inFIG. 39 was employed for the gate electrodes and the channels.

Cr and Al were deposited at respective thicknesses of 50 nm and 300 nmand then patterned, whereby three-system signal electrodes and drainelectrodes connected thereto were formed on one side of thecorresponding channels and three-system source electrodes, verticalconductor connection pad electrodes connected thereto and auxiliarycapacitor electrodes were formed on the other side of the correspondingchannels (see FIG. 40).

The portions of the n+a-Si layer between the sources and the drains wereremoved by etching selectively with respect to the channel protectivelayer with the signal electrodes used as masks. SiNx was deposited at athickness of 200 nm and its portions on the three-system verticalconductor connection pad electrodes, the peripheral pad electrodes, andthe source electrodes were removed by etching. An undercoat film forreflective electrode was formed by coating polyimide at a thickness of 2μm, and its portions on the three-system vertical conductor connectionpad electrodes were removed by etching. After the surface of thepolyimide film was subjected to dimple formation by mold thrusting, Alwas deposited at a thickness of 200 nm and patterned into a reflectivepixel electrode.

Then, to assemble a panel, steps that are the same as in the sixthembodiment of the present invention were executed, whereby a three-layerstack-type liquid crystal display panel having a sectional structure asshown in FIG. 38 was produced.

Driver ICs were mounted by TAB. When AC voltages having a maximum signalamplitude 5 V were applied between the three layers independentlyaccording to the timing chart shown in FIG. 26, the color reproductionperformance was insufficient. For example, the hue at the time of colordisplay was not constant, that is, it turned yellowish or, conversely,bluish, though a monochromatic contrast ratio of 5:1 was obtained.

Although the present invention has been described above in the form ofembodiments, the invention is not limited to those embodiments andvarious modifications are possible without departing from the spirit andscope of the invention.

According to the present invention, because the manner of the shieldelectrode connection and the potential application are improved, even ifscanning lines or signal lines exist in lower regions, the couplingbetween the pixel electrodes and those scanning lines or signal linescan be inhibited effectively. Therefore, the present invention canprovide a liquid crystal display device that is superior in displayperformance.

Further, because the stack order of the pixel electrodes and that of theauxiliary capacitance electrodes are made opposite to each other, theinfluences on the pixel electrodes through coupling can be minimized.Therefore, the present invention can provide a liquid crystal displaydevice that is superior in display performance.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is new and desired to be secured by letters patent of the UnitedStates is:
 1. A liquid crystal display comprising: a substrate; a firstelectrode for a pixel; a second electrode for said pixel; a thirdelectrode for said pixel; a common electrode; a first liquid crystallayer formed between said first electrode and said second electrode; asecond liquid crystal layer formed between said second electrode andsaid third electrode; a third liquid crystal layer formed between saidthird electrode and said common electrode; and a shield electrode forsaid pixel, said shield electrode being formed between said firstelectrode and said substrate, wherein electric potentials of said thirdelectrode and said shield electrode are substantially equal.
 2. A liquidcrystal display according to claim 1, further comprising a connectorconfigured to connect electrically said third electrode to said shieldelectrode.
 3. A liquid crystal display according to claim 1, wherein adifference between electric potentials of said third electrode and saidshield electrode is constant.
 4. A liquid crystal display according toclaim 1, further comprising an amplifier connected between said thirdelectrode and said shield electrode.
 5. A liquid crystal displayaccording to claim 1, further comprising a capacitor connected betweensaid third electrode and said shield electrode.
 6. A liquid crystaldisplay according to claim 1, wherein said shield electrode hassubstantially a same shape as said third electrode.
 7. A liquid crystaldisplay according to claim 1, wherein said shield electrode and saidthird electrode are configured to be operated dependently.
 8. A liquidcrystal display according to claim 1, further comprising: a firstpotential controller configured to control electric potentials of saidfirst electrode and said second electrode; and a second potentialcontroller configured to control electric potentials of said thirdelectrode and said shield electrode.
 9. A liquid crystal displayaccording to claim 8, wherein: said first controller is configured tofirst apply predetermined signals to said first and said second liquidcrystal layers and to then keep said first electrode and said secondelectrode floating; and said second controller is configured to applyelectric potentials to said third electrode and said shield electrode.10. A liquid crystal display according to claim 9, wherein said electricpotentials of said third electrode and said shield electrode aresubstantially equal.
 11. A liquid crystal display according to claim 9,wherein a difference between said electric potentials of said thirdelectrode and said shield electrode is constant.
 12. A liquid crystaldisplay comprising: a substrate; a first electrode for a pixel; a secondelectrode for said pixel; a third electrode for said pixel; a commonelectrode; a first liquid crystal layer formed between said firstelectrode and said second electrode; a second liquid crystal layerformed between said second electrode and said third electrode; a thirdliquid crystal layer formed between said third electrode and said commonelectrode; a first capacitance electrode formed between said firstelectrode and said substrate, and electrically connected to said firstelectrode; a second capacitance electrode formed between said firstcapacitance electrode and said substrate, and electrically connected tosaid second electrode; a third capacitance electrode formed between saidsecond capacitance electrode and said substrate, and electricallyconnected to said third electrode; and a common capacitance electrodeformed between said third capacitance electrode and said substrate, andconnected to a fixed electric potential; a first potential controllerconfigured to control electric potentials of said first electrode andsaid second electrode; and a second potential controller configured tocontrol electric potentials of said third electrode and said thirdcapacitance, wherein: said first capacitance electrode and said secondcapacitance electrode form a first auxiliary capacitor, said secondcapacitance electrode and said third capacitance electrode form a secondauxiliary capacitor, and said third capacitance electrode and saidcommon capacitance electrode form a third auxiliary capacitor.
 13. Aliquid crystal display according to claim 12, wherein: said firstcontroller is configured to first apply predetermined electricpotentials to said first and said second electrodes and to then keepsaid first electrode and said second electrode floating; and said secondcontroller is configured to apply electric potentials to said thirdelectrode and said third capacitance.
 14. A liquid crystal displaycomprising: a substrate; a first electrode for a pixel; a secondelectrode for said pixel; a third electrode for said pixel; a commonelectrode; a first liquid crystal layer formed between said firstelectrode and said second electrode; a second liquid crystal layerformed between said second electrode and said third electrode; a thirdliquid crystal layer formed between said third electrode and said commonelectrode; a first part electrode of a first capacitance for said pixel,electrically connected to said first electrode; a second part electrodeof said first capacitance for said pixel; a first part electrode of asecond capacitance for said pixel, electrically connected to said secondelectrode; a second part electrode of said second capacitance for saidpixel; a first part electrode of a third capacitance for said pixel,electrically fixed an electrical potential; a second part electrode ofsaid third capacitance for said pixel, formed between said firstelectrode and said first part electrode of said third capacitance,wherein electrical potentials of said second part electrode of saidfirst capacitance and said second part electrode of said secondcapacitance and said first part electrode of said third capacitance aresubstantially equal.
 15. A liquid crystal display according to claim 14,wherein: said second part electrode of said first capacitance is formedbetween said first electrode and said first part electrode of said firstcapacitance; and said second part electrode of said second capacitanceis formed between said first electrode and said first part electrode ofsaid second capacitance.
 16. A liquid crystal display according to claim14, wherein: said first part electrode of said first capacitance isformed between said first electrode and said second part electrode ofsaid first capacitance; and said first part electrode of said secondcapacitance is formed between said first electrode and said second partelectrode of said second capacitance.
 17. A liquid crystal displayaccording to claim 14, further comprising: connectors configured toconnect said second part electrode of said first capacitance and saidsecond part electrode of said second capacitance and said first partelectrode of said third capacitance.